Silver solder alloy



Patented Mar. 5, 1 940 PATENT OFFICE 2,192,455 SILVER; SOLDER. ALLOYJohann S. Streicher, Newark, N. J., assignor to American Platinum Works,Newark, N. J., a corporation of New Jersey No Drawing.

Application March 20, 1939,

Serial No. 263,048

3 Claims. 1 (Cl. 75-173) This invention relates in general to silveralloys and more particularly to silver alloys suitable for soldering orbrazing operations.

Silver solders in general use are based on the ternarysilver-copper-zinc eutectic alloy having a flow point of about 680 C.which in the easy flowing silver solder alloys is lowered to about 640,C. by the addition of cadmium, and the silver solders most generallyused thus com-' prise approximately 50% of silver, substantially equalparts of copper and zinc, and about 'l4%-18% cadmium.- Such solders areyellowish in color and have a further disadvantage in that the highvapor tension of the cadmium causes it to distill from the solder duringthe soldering operation at the melting point as well as at temperatureswithin 100 C. of its flow point, producing a change in the mechanicaland electrical properties and in the color of the alloy.

It is one object of the invention to produce a silver alloy particularlysuitable for use as a silver solder, having a high silver content, highcorrosion resistance and,high tensile strength, while at the same timehaving a low melting point .and 'a short melting range, enabling thealloys to flow freely and quickly when used as solders at the usualsoldering temperatures and permitting such alloys to be used inproducing strong solder joints at low temperatures with a minimum ofheat.

It is, a further object of the invention to produce a silver solderhaving a substantially white color and in which the distillation of thecadmium is substantially prevented.

I have found that the melting point of the silver-copper-zinc eutecticwhich forms the base of silver solders can be lowered by incorporatintherein up to not more than approximately '7 cadmium together with 1% to5% tin. My object is attained particularly when a larger amount ofcadmium is incorporated whenever a smaller amount of tin is used, andwhen a larger' amount of tin is incorporated whenever a smaller amountof cadmium is used. In the preferred embodiment of my invention 1,therefore, use at least approximately 5%, but not more thanapproximately 8%, of tin and cadmium combined.

With not more than about 7% cadmium, the cadmium content issubstantially protected against volatilization or distillation atsoldering temperatures, with the result that the harmful effectsaccompanying such distillation are avoided. The incorporation of up to5% tin in conjunction with the small percentage of cadmium serves tolower the melting point to the desired level. The alloys are practicallywhite, similar in color to platinum or palladium, particularly when theyhave a high tin content and a low 5 cadmium content; they are,therefore, especially useful for soldering white metals, such as nickel,or Monel metal. Their mechanical properties are as good as those of allthe other low melting silver solders. Their chemical properties, such 10as corrosion resistance, are superior to the solders in use and having ahigh cadmiumcontent. Since the new silver solders melt with a meltingrange of approximately 20 C. at the 1 extremely low flow points of 630C. respectively 640 0. they flow freely on any metal with which silversolders are used.

My alloys are best used in connection with fluxes having a melting pointbelow or close to k the melting point of the solder. In cases where theuse of fluxes is limited, I can obtain very effective solder joints whenI add minorquantitles of manganese or phosphorous to my alloys, forinstance in quantities between 0.2% and 2%. The addition of up to 2%manganese has the further advantage that while the flow point remainspractically unaffected the melting range is reduced to about 5 0., thusfurnishing ex-' tremely quickly flowing solders. Phosphorous andmanganese act as deoxidizers during the' soldering operation, and thepresence thereof in V quantities up to 2% shall not be excluded from thescope of the appended claims,

Specific embodiments of my invention comprise:

(1) An alloy of.

. Per cent Silver I 50 Zinc 20 Copper 22 40 Tin 1 Cadmium '7 having amelting range of 660 C. to 640 C.

(2) An alloy of- Per cent Silver Zinc 20 Copper 22 3 5o Cadmium 5 havinga melting range of 650 C. to 630 C.

The alloys may containlfrom approximately 48% to 56% silver, andfrom'approximately 20% to 22% copper, and from approximately 16% to outdeparting from the general scope herein indicated and denoted in theappended claims.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent, is:

1. A silver solder alloy comprising approximately 48% to 56% silver,approximately 20% to 22% copper, approximately 16% to 22% zinc,approximately 1% ,to 5% tin and approximately 1% to 7% cadmium.

2. A silver solder alloy comprising approximately 48% to 56% silver,approximately 20% to 22% copper, approximately 16% to 22% zinc,approximately 1% to 5% tin, and approximately 7% to 1% cadmium, and inwhich the combined tin and cadmium content does not fall below about 5%and does not exceed about 8%.

3. A silver solder alloy which comprises about 50% silver, about 22%copper, about 20% zinc, and about 7% cadmium and about 1% tin.

J OHANN S. S'I'REICBER.

